1. Field of the Invention
The invention relates to apparatus and methods for controlling process and material parameters of pulp in a paper making machine and in particular to pulp flowing into a paper machine headbox.
2. Description of Related Technology
A headbox of a paper machine may be divided into sections by walls spaced across the width of the machine in order to allow for independent control in each section of various properties of the paper pulp suspension, such as pulp density and fiber orientation.
Such a sectioned headbox for a paper making machine is disclosed in DE 40 19 593. In such a device, a plurality of pulp feeds are fed to a headbox which has a forming unit divided into sections over a width thereof. The properties of the pulp suspension in the individual feed lines or channels can be influenced by mixing two pulp suspension streams of different properties and different throughputs.
A disadvantage of the headbox disclosed in DE 40 19 593 is that it requires two ready reserves of a pulp suspension, each reserve of substantially constant composition. Another disadvantage is that when the pulp suspension properties of a section are adjusted for the purpose of influencing a single given suspension property, other properties of the pulp suspension typically change in the same ratio.